Self-Calibrated Laser-Induced Breakdown Spectroscopy for the Quantitative Elemental Analysis of Suspended Volcanic Ash.

Real-time analysis of fine ash in volcanic plumes, which represent magma fragments expelled from the crater during explosive eruptions, is a valuable tool for volcano monitoring and hazard assessment. To obtain the chemical characterization of the juvenile pyroclastic material emitted in volcanic plumes, many analytical techniques can be used. Among them, laser-induced breakdown spectroscopy (LIBS) is the one that can most easily be adapted to advanced applications in extreme environments. In this paper, LIBS experiments based on self-calibrated approaches are used to determine the elemental composition of suspended volcanic ash. To simulate the conditions of dispersed volcanic ash in the atmosphere, different sizes of volcanic ash samples are suspended in the air by laser-induced shockwaves in a dedicated chamber, and a parametric study is carried out to establish the optimal experimental conditions for recording usable plasma emission spectra for each ash size. The quantitative analysis is performed using a self-calibrated analytical method, including calibration-free LIBS, which is based on the calculation of the spectral radiance of a uniform plasma in local thermodynamic equilibrium. The method accounts intrinsically for self-absorption since it modifies the intensity of spectral lines and thus leads to an underestimation of the elemental fraction. An intensity calibration of the spectra based on the measurements of Fe lines intensities was also used in this work to deduce the apparatus response from the spectrum itself and avoid the use of standard calibration lamps. Results demonstrate the potential of real-time measurements of elemental fractions in volcanic ash with good agreement with the literature composition.

Simple derivation of L-absorption spectra of 3d transition metal elements by the self-absorption effect observed in soft X-ray emission spectra.

This study proposes a simple evaluation method for deriving L-absorption information from two L-emission spectra of 3d transition metal (TM) elements obtained at two different accelerating voltages. This method realizes a spatial identity for X-ray emission and absorption spectroscopies. This method was evaluated for the Fe L-emission spectra of Fe and its oxides, and was applied to the TM L-emission spectra of MnO, Co, CoO, and NiO. The derived absorption peak positions were consistent with those obtained previously at synchrotron orbital radiation facilities, which considered the core-hole effect. This simple derivation method could be useful for obtaining X-ray absorption spectroscopy distribution images from X-ray emission spectroscopy mapping data obtained by scanning electron microscopy.

Validity Evidence for the Self-Absorption Scale (SAS) in Spanish Population / Evidencias de Validez de la Escala de Autoabsorción (SAS) en Población Española

Background: The Self-Absorption Scale (SAS) is one of the few instruments that measure dysfunctional self-focused attention or self-absorption, a transdiagnostic factor of vulnerability to various emotional disorders. The internal structure of the Spanish version of the SAS and its relationship with other variables have not been examined, nor has whether its subscales provide relevant information. These were the two goals of the present study. Method: The factor structure of the SAS, its internal consistency, and its relationship with depression and post-traumatic stress were analyzed in a Spanish community sample of 519 adults. Results: The SAS presented a symmetrical bifactor structure with a general factor of self-absorption that explained most of the variance in the items and two specific factors of private and public self-absorption. The total scale and the two subscales of the SAS exhibited excellent, good or adequate reliability coefficients (alphas/omegas = .70 – .88) and correlated with depression and post-traumatic stress (r = .34 – .46). Conclusions: The SAS provides reliable, valid measures of dysfunctional self-focused attention in Spanish adults, but its Private and Public Self-absorption subscales are not much more useful than the information provided by its total scale.(AU)

Antecedentes: la Escala de Autoabsorción (SAS) es uno de los pocos instrumentos que mide la atención autofocalizada disfuncional o autoabsorción, un factor transdiagnóstico de vulnerabilidad a diversos trastornos emocionales. La estructura interna de la versión española de la SAS y su relación con otras variables no han sido examinadas, ni tampoco si sus subescalas aportan información relevante. Estos fueron los objetivos del presente estudio. Método: se analizó la estructura factorial de la SAS, su consistencia interna y la relación con la sintomatología depresiva y de estrés postraumático en una muestra comunitaria española de 519 adultos. Resultados: la SAS presentó una estructura bifactor simétrica con un factor general de autoabsorción que explicaba la mayoría de la varianza de los ítems y dos factores específicos de autoabsorción privada y pública. La escala total y las dos subescalas mostraron coeficientes de fiabilidad excelentes, buenos o adecuados (alfas/omegas = .70 – .88) y correlacionaban con la depresión y el estrés postraumático (r = .34 – .46). Conclusiones: la SAS proporciona medidas fiables y válidas de la atención autofocalizada disfuncional en adultos españoles, pero sus subescalas de autoabsorción privada y pública pueden no ser muy útiles más allá de la información proporcionada por su escala total.(AU)

Caught on the surface: Tustin on autistic experience.

According to Frances Tustin, the core of autism is found in sensory modifications-and tactile modifications in particular. Tustin argues that sensory experiences may become self-absorbed to such an extent that the sensory environment experientially flattens into a two-dimensional "feel," which complicates the individual's relations with the external environment and other people. Focusing on these fundamental modifications and their experiential consequences, the article introduces Tustin's main insight in terms of collapse of intentional depth, suggesting that this collapse concerns not only concrete spatial depth, but symbolic and intersubjective depth as well. By so doing, the article illustrates how Tustin's ideas render intelligible certain commonly recognized features of autism, such as "deficits in the ability to initiate and to sustain reciprocal social interaction and social communication" and "restricted, repetitive, and inflexible patterns of behavior, interests or activities" (ICD-11).

Improving X-ray Scintillating Merits of Zero-Dimensional Organic-Manganese(II) Halide Hybrids via Enhancing the Ligand Polarizability for High-Resolution Imaging.

Luminescent metal halides have been exploited as a new class of X-ray scintillators for security checks, nondestructive inspection, and medical imaging. However, the charge traps and hydrolysis vulnerability are always detrimental to the three-dimensional ionic structural scintillators. Here, the two zero-dimensional organic-manganese(II) halide coordination complexes 1-Cl and 2-Br were synthesized for improvements in X-ray scintillation. The introduction of a polarized phosphine oxide can help to increase the stabilities, especially the self-absorption-free merits of these Mn-based hybrids. The X-ray dosage rate detection limits reached up to 3.90 and 0.81 µGyair/s for 1-Cl and 2-Br, respectively, superior to the medical diagnostic standard of 5.50 µGyair/s. The fabricated scintillation films were applied to radioactive imaging with high spatial resolutions of 8.0 and 10.0 lp/mm, respectively, holding promise for use in diagnostic X-ray medical imaging.

Spectroscopic and crystallographic analysis of nephrite jade gemstone using laser induced breakdown spectroscopy, Raman spectroscopy, and X-ray diffraction.

The elemental composition, mineral phases, and crystalline structure of nephrite jade were investigated using calibration-free laser-induced breakdown spectroscopy (CF-LIBS), Raman spectroscopy, and X-ray diffraction (XRD). For compositional analysis, the laser-induced plasma was generated on the surface of nephrite jade. The plasma emissions were then acquired and analyzed, which revealed several elements in the sample, including Si, Mg, Ca, Li, Fe, Al, Na, K, and Ni. The plasma temperature was extracted from the Boltzmann plot before and after two-step self-absorption correction, and used in CF-LIBS calculations to get the elemental concentration. After self-absorption correction, the quantitative results obtained using CF-LIBS were found to be in close agreement with ICP-OES. The Raman spectrum of nephrite jade exhibits Si-O and M-OH stretching vibrations in the regions of 100 cm-1 to 1200 cm-1 and 3600 cm-1 to 3700 cm-1, respectively, whereas the XRD spectrum revealed the monoclinic crystalline phase of tremolite.

Establishment and validation of a prediction model for self-absorption probability of chronic subdural hematoma.

Background: Chronic subdural hematoma (CSDH) is common in elderly people with a clear or occult traumatic brain injury history. Surgery is a traditional method to remove the hematomas, but it carries a significant risk of recurrence and poor outcomes. Non-surgical treatment has been recently considered effective and safe for some patients with CSDH. However, it is a challenge to speculate which part of patients could obtain benefits from non-surgical treatment. Objective: To establish and validate a new prediction model of self-absorption probability with chronic subdural hematoma. Method: The prediction model was established based on the data from a randomized clinical trial, which enrolled 196 patients with CSDH from February 2014 to November 2015. The following subjects were extracted: demographic characteristics, medical history, hematoma characters in imaging at admission, and clinical assessments. The outcome was self-absorption at the 8th week after admission. A least absolute shrinkage and selection operator (LASSO) regression model was implemented for data dimensionality reduction and feature selection. Multivariable logistic regression was adopted to establish the model, while the experimental results were presented by nomogram. Discrimination, calibration, and clinical usefulness were used to evaluate the performance of the nomogram. A total of 60 consecutive patients were involved in the external validation, which enrolled in a proof-of-concept clinical trial from July 2014 to December 2018. Results: Diabetes mellitus history, hematoma volume at admission, presence of basal ganglia suppression, presence of septate hematoma, and usage of atorvastatin were the strongest predictors of self-absorption. The model had good discrimination [area under the curve (AUC), 0.713 (95% CI, 0.637-0.788)] and good calibration (p = 0.986). The nomogram in the validation cohort still had good discrimination [AUC, 0.709 (95% CI, 0.574-0.844)] and good calibration (p = 0.441). A decision curve analysis proved that the nomogram was clinically effective. Conclusions: This prediction model can be used to obtain self-absorption probability in patients with CSDH, assisting in guiding the choice of therapy, whether they undergo non-surgical treatment or surgery.

Simple defocus laser irradiation to suppress self-absorption in laser-induced breakdown spectroscopy (LIBS).

This study introduces a novel and simple way to suppress the self-absorption effect in laser-induced breakdown spectroscopy (LIBS) by utilizing a defocusing laser irradiation technique. For this purpose, a Nd:YAG laser with a wavelength of 1,064 nm and repetition rate of 10 Hz with energy in the range of 10 mJ-50 mJ was used. The laser irradiation was focused by using a 150-mm-focal-length plano-convex lens onto the sample surface under defocusing of approximately -6 mm. Potassium chloride (KCl) and sodium chloride (NaCl) pellet samples were used to demonstrate this achievement. When the defocus position is adjusted to -6 mm for KCl and NaCl samples, the self-reversal in the emission lines of K I 766.4 nm, K I 769.9 nm, Na I 588.9 nm, and Na I 589.5 nm vanish. Meanwhile, the FWHM values of K I 766.4 and K I 769.9 nm are 0.29 nm and 0.23 nm, respectively, during -6 mm defocus laser irradiation, as opposed to 1.24 nm and 0.86 nm under tight focus laser irradiation. Additionally, this work demonstrates that, when the laser energy is changed between 10 and 50 mJ, no self-reversal occurs in the emission lines when -6 mm defocus laser irradiation is applied. Finally, a linear calibration curve was generated using KCl at a high concentration ranging between K concentrations from 16.6% to 29%. It should be noted that, even at such high K concentrations, the calibration curve is still linear. This means that self-absorption is almost negligible. This simple change in defocus laser irradiation will undoubtedly contribute to the suppression of the self-absorption phenomenon, which disrupts LIBS analytical results.

Improvements in the radiochemical method for separating 226Ra in solid samples through coprecipitation with BaSO4.

The aim of this work was to improve the commonly used method for 226Ra determination in water and to establish its application in solid samples. This method is based on the coprecipitation of Ra with BaSO4 and gross alpha counting of the precipitate. An exhaustive study of the coprecipitation behaviour of the most abundant cations present in solid samples was performed to avoid incorrect radiochemical yields. As a result, it was considered necessary to introduce two new purification steps into the conventional method. Likewise, two nuclides, 241Am and 226Ra, were compared to obtain the mass efficiency curve given their different behaviour in the coprecipitation process. While Ra behaves similarly to Ba, Am coprecipitates, forming mixed crystals that may behave differently in the self-absorption process. The influence of the cations on the chemical yield with no precipitate purification was: Sr2+≫Fe3+>Mg2+≈Ca2+>K+≈Na+. The method was successfully applied to soil, sediment, and plant ash samples.

All-Inorganic Manganese-Based CsMnCl3 Nanocrystals for X-Ray Imaging.

Lead-based halide perovskite nanomaterials with excellent optical properties have aroused great attention in the fields of solar cells, light-emitting diodes, lasing, X-ray imaging, etc. However, the toxicity of lead prompts researchers to develop alternatives to cut down the usage of lead. Herein, all-inorganic manganese-based perovskite derivatives, CsMnCl3 nanocrystals (NCs), with uniform size and morphology have been synthesized successfully via a modified hot-injection method. These NCs have a direct bandgap of 4.08 eV and a broadband emission centered at 660 nm. Through introducing modicum lead (1%) into the CsMnCl3 NCs, the photoluminescence intensity greatly improves, and the quantum yield (PLQY) increases from 0.7% to 21%. Furthermore, the CsMnCl3 :1%Pb NCs feature high-efficiency of X-ray absorption and radioluminescence, which make these NCs promising candidates for X-ray imaging.

Analytical technique for self-absorption structure of iron L-emission spectra obtained by soft X-ray emission spectrometer.

The method deriving the L self-absorption spectrum from Lα,ß emission spectra obtained at different accelerating voltages has been optimized for analyzing the chemical state of Fe in solid materials. Fe Lα,ß emission spectra obtained are fitted using Pseudo-Voigt functions and normalized by the integrated intensity of each Fe Ll line, which is not affected by L2,3 absorption edge. The self-absorption spectrum is calculated by dividing the normalized intensity profile collected at low accelerating voltage by that collected at a higher accelerating voltage. The obtained profile is referred to as soft X-ray self-absorption structure (SX-SAS). This method is applied to six Fe-based materials (Fe metal, FeO, Fe3O4, Fe2O3, FeS and FeS2) to observe different chemical states of Fe in those materials. By comparing the self-absorption spectra of iron oxides, one can observe the L3 absorption peak structure shows a shift to the higher energy side as ferric (3+) Fe increases with respect to ferrous (+2) Fe. The intensity profiles of self-absorption spectra of metallic Fe and FeS2 shows shoulder structures between the L3 and L2 absorption peaks, which were not observed in spectra of Fe oxides. These results indicate that the SX-SAS technique is useful to examine X-ray absorption structure as a means to understand the chemical states of transition metal elements.

A new route to obtain fluorescence X-ray absorption spectra of compounds and to remove the self-absorption induced nonlinearity in the spectra.

A new route to obtain fluorescence X-ray absorption spectra of compounds and to remove the self-absorption induced nonlinearity in the spectra is described. The fluorescent intensity If is linearly proportional to the absorption coefficient µ. For studies of surface structures around an element (κ) the fluorescence detection is often the mode of choice. However, the measurement may suffer from a self-absorption (SA) effect which nonlinearly distorts the spectra. The effect is severe when κ is concentrated or the measurements are carried out in certain geometries. Here, the correlations among emission events in compounds are examined following resonance X-ray core-electron excitation within κ. Under conditions leading to SA, If emitted from κ apparently has a conjugated relationship with the fluorescent intensities simultaneously emitted from other elements (ξ). Normalizing the former (κ) by the latter (ξ) will largely remove SA effects and reduce this nonlinear problem to a tractable linear problem. This does result in a moderate reduction of the spectral amplitude due to the so-called secondary emission from ξ excited by the emission from κ. Nonetheless, the resulting spectra will allow one to accurately determine bond distances and disorder and, in some respects, can be superior to spectra obtained via the absorption channel. For µξ < µκ and grazing incidence geometry, the amplitude reduction can be small and simple normalization is sufficient to restore the spectral integrity with remarkable accuracy. This has been instrumental in unravelling the surface and subsurface structures around cations in amorphous Ga-In-O and Zn-Sn-O films which are otherwise inaccessible due to severe SA effects. This method has also been applied to several samples with µξ ≃ µκ to examine its applicability. For these samples, the amplitude reduction is 12 ± 4% versus their standards for the data measured with the classical 45°/45° geometry. This experimental method is easy to implement. Since If from κ and ξ are measured by the same detector system, it is also superior to other methods in removing systematic errors such as detector system nonlinearity, electronic noise, and some beam instabilities, and in removing spectral imperfections due to, for example, SA effects, diffraction effects and sample inhomogeneity. The distortions resulting from the latter can be severe in the spectra measured in transmission mode.

Quantitation improvement of underwater laser induced breakdown spectroscopy by using self-absorption correction based on plasma images.

Laser-induced breakdown spectroscopy (LIBS) is a practical technique for in-situ detection, but self-absorption effect has been a big issue for quantitative applications of this technique. In presented work, a method was developed to correct self-absorption to improve the quantitation of underwater LIBS. We proposed "relative self-absorption coefficient" as the critical parameter to evaluate self-absorption, and the plasma image was employed as the reference to determine the coefficient value. Based on that, the LIBS detection was successfully corrected by the coefficient to realize quantitative analysis, and the "Dominant Factor-PLS" was used as assistance. The results indicated that our method greatly improved LIBS quantitation in practice. More importantly, the calibration curve was able to be established with high linearity (R2 = 0.9999) to cover a large concentration range (0-103 ppm). It is hoped that our method could be a contribution to developing LIBS as an analytical tool for field measurements.

Electron Probe Microanalysis of Transition Metals using L lines: The Effect of Self-absorption.

Electron microprobe-based quantitative compositional measurement of first-row transition metals using their L$\alpha$ X-ray lines is hampered by, among other effects, self-absorption. This effect, which occurs when a broad X-ray line is located close to a broad absorption edge, is not accounted for by matrix corrections. To assess the error due to neglecting self-absorption, we calculate the L$\alpha$ X-ray intensity emitted from metallic Fe, Ni, Cu, and Zn targets, assuming a Lorentzian profile for the X-ray line and taking into account the energy dependence of the mass absorption coefficient near the absorption edge. We find that calculated X-ray intensities depart increasingly, for increasing electron beam energy, from those obtained assuming a narrow X-ray line and a single fixed absorption coefficient (conventional approach), with a maximum deviation of $\sim$15% for Ni and of $\sim$10% for Fe. In contrast, X-ray intensities calculated for metallic Zn and Cu do not differ significantly from those obtained using the conventional approach. The implications of these results for the analysis of transition-metal compounds by electron probe microanalysis as well as strategies to account for self-absorption effects are discussed.

The Processing of Visual Signals in Major Depressive Disorder.

The balanced processing of the internal mental world and the external world is a crucial aspect of everyday well-being. An extensive control of the internal emotional and cognitive world that often results in an internal expression of distress is a common feature of internalizing disorders. However, how depression affects the processing of the external world is still an open question. We, therefore, tested the processing of visual signals in major depressive disorder (MDD). To this end, we recorded the electroencephalogram of 38 MDD patients and 38 controls, while they performed a response-choice task with informative feedback and a passive viewing task. MDD patients differed significantly from controls in the early information processing of visual stimuli. The vertex positive potential (VPP) evoked by feedback in the response-choice task and pictures in the passive viewing task were smaller in MDD patients than in controls. This outcome suggests that depression might subtract attentional resources from external signal processing, with potential consequences in various cognitive domains.

A method for improving the accuracy of calibration-free laser-induced breakdown spectroscopy by exploiting self-absorption.

The existence of the self-absorption effect results in a nonlinear relationship between spectral intensity and elemental concentration, which dramatically affect the quantitative accuracy of laser-induced breakdown spectroscopy (LIBS), especially calibration-free LIBS (CF-LIBS). In this work, the CF-LIBS with columnar density and standard reference line (CF-LIBS with CD-SRL) was proposed to improve the quantitative accuracy of CF-LIBS analysis by exploiting self-absorption. Our method allows using self-absorbed lines to perform the calibration-free approach directly and does not require self-absorption correction algorithms. To verify this method, the experiment was conducted both on aluminium-bronze and aluminium alloy samples. Compared with classical CF-LIBS, the average errors (AEs) of CF-LIBS with CD-SRL were decreased from 3.20%, 3.22%, 3.15% and 3.01%-0.95%, 1.00%, 1.16% and 1.78%, respectively for four aluminium-bronze alloy samples. The AEs were decreased from 0.66%, 0.70%, 0.89% and 1.30%-0.43%, 0.61%, 0.77% and 0.33%, respectively for four aluminium alloy samples. The experimental results demonstrated that CF-LIBS with CD-SRL provided higher quantitative accuracy and stronger adaptability than classical CF-LIBS, which is quite helpful for the practical application of CF-LIBS.

Measurement error due to self-absorption in calibration-free laser-induced breakdown spectroscopy.

Self-absorption of spectral lines is known to lower the performance of analytical measurements via calibration-free laser-induced breakdown spectroscopy. However, the error growth due to this effect is not clearly assessed. Here we propose a method to quantify the measurement error due to self-absorption based on the calculation of the spectral radiance of a plasma in local thermodynamic equilibrium. Validated through spectroscopic measurements for a binary alloy thin film of compositional gradient, the method evidences that measurement performance lowering due to self-absorption depends on the spectral shape of the analytical transition and on the intensity measurement method. Thus, line-integrated intensity measurements of Stark broadened lines enable accurate analysis, even at large optical thickness, if line width and plasma size are precisely known. The error growth due to self-absorption is significantly larger for line shapes dominated by Doppler broadening and for line-center intensity measurements. The findings present a significant advance in compositional measurements via calibration-free laser-induced breakdown spectroscopy, as they enable straightforward selection of most appropriate analytical lines.

Associations between self-absorption and working memory capacity: A preliminary examination of a transdiagnostic process spanning across emotional disorders.

Considered a transdiagnostic process spanning across emotional disorders, self-absorption reflects self-focused processing that is excessive, sustained, and inflexible. Working memory capacity is critical for self-regulation, inclusive of mitigating perseverative thinking. Providing the first known examination of associations between self-absorption and working memory capacity, a negative association was expected. A sample of adults (N = 63; 70 % experiencing an anxiety or depressive disorder) completed the study protocol, which included completing a structured diagnostic interview, self-report measures, and a working memory capacity task. Self-absorption, as predicted, negatively correlated with working memory capacity, with an association found for the private, but not public, aspect of self-absorption. The association between private self-absorption and working memory capacity was not attributable to shared variance with public self-absorption or negative affectivity. Diagnostic status (anxiety disorder, depressive disorder, or either disorder) did not moderate the association. The results provide evidence that self-absorption relates to impairments in working memory capacity. Implications and future directions for how these results advance our understanding and treatment efforts of self-absorption are discussed.

Investigation of 18F and 89Zr Isotopes Self-Absorption and Dose Rate Parameters for PET Imaging.

This work concerns study of self-absorption factor (SAF) and dose rate constants of zirconium-89 (89Zr) for the purpose of radiation protection in positron emission tomography (PET) and to compare them with those of 18F-deoxyglucose (18F-FDG). We analyzed the emitted energy spectra by 18F and 89Zr through anthropomorphic phantom and calculated the absorbed energy using Monte Carlo method. The dose rate constants for both radionuclides were estimated with 2 different fluence-to-effective dose conversion coefficients. Our estimated SAF value of 0.65 for 18F agreed with the recommendation of the American Association of Physicists in Medicine (AAPM). The SAF for 89Zr was in the range of 0.61-0.66 depending on the biodistribution. Using the fluence-to-effective dose conversion coefficients recommended jointly by the American National Standards Institute and the American Nuclear Society (ANSI/ANS), the dose rate at 1 m from the patient for 18F was 0.143 µSv·MBq-1·hr-1, which is consistent with the AAPM recommendation, while that for 89Zr was 0.154 µSv·MBq-1·hr-1. With the conversion coefficients currently recommended by the International Committee on Radiological Protection (ICRP), the dose rate estimates were lowered by 2.8% and 2.6% for 89Zr and 18F, respectively. Also, we observed that the AAPM derived dose is an overestimation near the patient, compared to our simulations, which can be explained by the biodistribution nature and the assumption of the point source. Thus, we proposed new radiation protection factors for 89Zr radionuclide.

Branching Ratio Method for Assessing Optically Thin Conditions in Laser-Induced Plasmas.

The branching ratio method is usually used to evaluate the optical thinness conditions in laser-generated plasmas, which are important for the application of analytical methods such calibration free laser induced breakdown spectroscopy (CF-LIBS). In this communication, we warn on the possibility that in some circumstances, the branching-ratio method might give results close to the one characterizing optically thin plasma conditions, even in the presence of a substantial self-absorption for the transitions considered.